Many oil wells require pumping in order to produce the well fluid. One common type employs a reciprocating downhole pump. A sucker rod extends down the well to the plunger of the pump. A lifting mechanism at the surface strokes the sucker rod to lift the well fluid. Extending a sucker rod string down to a pump is problematic for deep wells and wells where the pump is located in an inclined lower portion.
Rotary pumps driven by a downhole electrical motor are also utilized to a large extent. The pump may be a centrifugal pump having many stages of impellers and diffusers. Rotary oil well pumps also include progressing cavity pumps, in which a rotor rotates within an elastomeric stator. The rotor and the stator have helical contours.
Also, various proposals have been made to drive a reciprocating pump with a downhole electrical motor. One type employs a motor that rotates a drive shaft. A helical screw mechanism converts the rotation to linear to stroke the pump. In another type proposed, a linear motor is employed to stroke the pump. The linear motor has electromagnet coils and a mover with permanent magnets located within a bore of the coil assembly. When energized with one type of pulse, the mover strokes linearly in one direction. Another type of pulse causes the mover to stroke in an opposite direction.
For various reasons, reciprocating pumps with downhole electrical motors are not in commercial use to any extent.